Devices with covering layer and filler

ABSTRACT

A method of manufacturing a device includes forming a covering layer having affinity for a filler to be injected into a space between a first base and a second base, on at least one of the opposing surfaces of the first base and the second base, and then injecting the filler into the space between the first base and the second base.

This application is based upon and claims the benefit of priority fromJapanese patent application No. 2010-137879, filed on Jun. 17, 2010, thedisclosure of which is incorporated herein in its entirety by reference.

BACKGROUND OF THE INVENTION

This invention relates to a method of a manufacturing a device, and inparticular to a method of manufacturing a semiconductor device involvingan underfill injection process.

When a semiconductor device has a semiconductor chip mounted on amounting board, or a semiconductor device is formed by stacking aplurality of semiconductor chips, a resin material called “underfill” isinjected into a space between the board and the semiconductor chip orbetween the stacked semiconductor chips and cured in order to protectbumps, to enhance the connection strength, and to improve the moistureresistance.

In general, a side-fill method utilizing capillary action is employed toinject an underfill material (filler). However, as the degree ofintegration within a semiconductor device increases, the gap between aboard and a semiconductor chip or between semiconductor chips becomessmaller, which leads to various problems, including increased timerequired for the injection, generation of voids in the injected resin,and unwanted interruption of the injection process.

In order to solve these problems, Japanese Laid-Open Patent PublicationNo. 2007-59441 (Patent Document 1) proposes to plasma treat, with N₂gas, the surface of at least one of the semiconductor chip and themounting board before injecting the underfill material into the spacebetween the mounting board and the semiconductor chip. It is claimedthat, according to this method, the angle of contact between theepoxy-based underfill material and a passivation film becomes smaller,and hence the wettability of the underfill material with the passivationfilm is improved, resulting in improved filling property of theunderfill material.

SUMMARY

However, the present inventor recognized that the plasma treatment asdescribed in Patent Document 1 may lead to a problem that a device inthe semiconductor chip is electrically broken.

Describing in more detail, there are formed, on the surface of thesemiconductor chip, a multiplicity of electrically conductive bumpsconnected to internal through electrodes. When exposed to plasma, thesebumps serve as antennas to collect electric charge contained in theplasma. The electric charge collected by the bumps flows into the devicewithin the semiconductor chip via the through electrodes connected tothe bumps. The device will be broken if a large amount of electriccharge flows into the device. Thus, the plasma treatment of thesemiconductor chip may lead to a problem of electrical breakdown of thedevice in the semiconductor chip.

This invention seeks to solve the problem at least in part.

In one embodiment, there is provided a device that includes: a firstbase; a second base arranged above the first base to leave a space; afiller disposed in the space; and a covering layer formed on at leastone of the opposing surfaces of the first base and the second base, andhaving affinity for the filler.

In another embodiment, there is provided a semiconductor device thatincludes: a first substrate; a second substrate that is stacked over thefirst substrate via a bump electrode to form a gap between the firstsubstrate and the second substrate; a resin layer that is formed in thegap; and a first covering layer that is intervening between the resinlayer and the first substrate. In the device, the first covering layeris higher in wettability with respect to the resin layer than the firstsubstrate.

In still another embodiment, there is provided a semiconductor devicethat includes: a stack structure including a plurality of substratesstacked over with one another via a bump electrode to form gaps betweenadjacent ones of the plurality of substrates; a resin layer that isformed in the gaps; and a covering layer that is intervening between theresin layer and adjacent ones of the plurality of substrates.

BRIEF DESCRIPTION OF THE DRAWINGS

The above features and advantages of the present invention will be moreapparent from the following description of certain preferred embodimentstaken in conjunction with the accompanying drawings, in which:

FIGS. 1A to 1D are process charts for explaining a semiconductor devicemanufacturing method according to a first embodiment of this invention;

FIG. 2 is a model diagram illustrating a covering layer formed by thesemiconductor device manufacturing method according to the firstembodiment of the invention;

FIG. 3 is a diagram illustrating a schematic configuration of a CVDsystem that can be used to form the covering layer;

FIG. 4 is a diagram illustrating a schematic configuration of asupercritical deposition system that can be used to form the coveringlayer;

FIG. 5A is a diagram illustrating a state of a semiconductor devicebefore injection of underfill according to a second embodiment of thisinvention; and

FIG. 5B is a diagram illustrating a state in which the underfill hasbeen injected into the semiconductor device of FIG. 5A.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The invention will be now described herein with reference toillustrative embodiments. Those skilled in the art will recognize thatmany alternative embodiments can be accomplished using the teachings ofthe present invention and that the invention is not limited to theembodiments illustrated for explanatory purposes.

The description will start with principles of this invention.

A side-fill method, which is used to inject an underfill material,utilizes capillary action. The capillary action is caused by surfacetension of liquid entering into a capillary tube and wettability of awall surface to the liquid, as expressed by the following generalformula (when the liquid in a tubular object moves upward):h=2T cos θ/ρgrwhere h denotes a height to which the liquid level rises, T denotes asurface tension, θ denotes a contact angle (parameter for determiningwettability), ρ denotes a liquid density, g denotes a gravityacceleration, and r denotes an inner diameter of the tube.

As is seen from the formula above, the height h to which the liquidlevel is caused to rise by the capillary action can be increased byreducing the contact angle that is a parameter for determining thewettability. This means that injection of the underfill material(filler) can be made easier by improving the wettability of the surfacesof the semiconductor chip and the mounting board to a resin materialused for the underfill. According to this invention, therefore, thewettability is improved by forming, before injection of the underfillmaterial, a covering film having a region with affinity for theunderfill material on the surface(s) of the semiconductor chip or (and)the mounting board.

Next, referring to FIGS. 1A to 1D, a semiconductor device manufacturingmethod according to a first embodiment of this invention will bedescribed.

At first, first and second bases 11 and 12 are provided. As shown inFIG. 1A, the second base 12 is arranged above the first base 11. Thereis formed between the first base 11 and the second base 12 a space 13,which is to be filled with an underfill material. The first base 11 maybe, for example, a mounting board, and the second base 12 may be, forexample, a semiconductor chip mounted on the mounting board. There are aplurality of bumps 14 between the mounting board and the semiconductorchip, and these bumps 14 electrically connect the mounting board and thesemiconductor chip. The presence of the bumps 14 forms the space 13between the mounting board and the semiconductor chip, which is to befilled with the underfill material.

Next, as shown in FIG. 1B, a covering layer 15 having a region withaffinity for the underfill material is formed (deposited) on thesurfaces exposed to the space 13. Then, the surfaces exposed to thespace 13 is coated with the covering layer 15. The covering layer 15 maybe a molecular layer or a thin film. Formation of the covering layer 15may be carried out by using various methods such as an evaporationmethod, a chemical vapor deposition (CVD) method, and a supercriticaldeposition method.

FIG. 2 is a diagram showing a model of a molecular layer forming thecovering layer 15. As shown in FIG. 2, the covering layer 15 desirablyhas a region 21 which has affinity for or can be combined with thesurface of the first base 11 or the second base 12, and a region 22which has affinity for or can be combined with the underfill material.

Then, as shown in FIGS. 1C and 1D, the underfill material (resinmaterial) 16 is injected into the space 13 between the first base 11 andthe second base 12 by means of a side-fill method.

Since the surfaces exposed to the space 13 are coated with the coveringlayer 15 having affinity for the underfill material 16, the underfillmaterial 16 is allowed to enter the space 13 rapidly or easily. Thismeans that, even if the gap between the first base 11 and the secondbase 12 is so small that the underfill material 16 is inhibited fromentering the gap, the underfill material 16 is allowed to enter the gapeasily by virtue of the provision of the covering layer 15 according tothis embodiment of the invention. Further, generation of voids can beprevented or suppressed even if the surface of the first base 11 or thesecond base 12 is formed of a material which is incompatible with orwhich has low wettability to the underfill material 16.

Finally, the underfill material 16 is heated and cured.

In this manner, a semiconductor device is obtained in which the secondbase 12 is mounted on the first base 11 and the space between the firstand second bases is filled with the underfill. The underfill materialmay be an epoxy resin mixed with a curing agent. The covering layer 15may be formed not only of the epoxy resin having no curing agent addedthereto, but also may be formed of polyimide. Components of the coveringlayer 15 are determined in consideration of materials of the surfaces ofthe first base and the second base, and composition of the underfillmaterial. A material for the covering layer 15 is selected which has aregion with affinity for the first base and the second base and a regionwith affinity for the underfill material.

According to this embodiment, as described above, a covering layerhaving affinity for the filler which is injected between the first andsecond bases is preliminarily formed on at least one of the opposingsurfaces of the first and second bases. Even if either the first base orthe second base is a semiconductor chip, unlike plasma treatment, nodevice built in the semiconductor chip will be electrically broken inthis process. Therefore, this method is capable of improving thewettability of the surface of at least either the first base or thesecond base to the resin material without the risk of electricalbreakdown.

Next, formation of the covering layer 15 will be described in furtherdetail with reference to FIG. 3. Description here will be made of a casein which a polyimide film is formed as the covering layer 15, using aCVD method.

As shown in FIG. 3, a CVD system has a vacuum chamber 31, a load locksystem 32, an exhaust system 33, and a heater 34. The vacuum chamber 31has therein a sample holder 35 and two raw material vaporizers 36, eachhaving a heater.

A base 37 to be treated is introduced into the vacuum chamber 31 throughthe load lock system 32, and held by the sample holder 35. The base 37as used herein may be the first base 11 or the second base 12, or astructure in which the second base 12 is mounted on the first base 11.This means that the formation of the covering layer 15 may be carriedout either before or after the second base 12 is mounted on the firstbase 11. Further, the covering layer 15 need not necessarily be formedon both of the opposing surfaces of the first base 11 and the secondbase 12, but may be formed only on either one of the surfaces that haspoorer compatibility or wettability with respect to the underfillmaterial.

PMDA (Pyromellitic Dianhydride) and ODA (4,4′-diamino-diphenyl ether, or4,4′-oxydianiline) as raw materials for the covering layer 15 are placedin the two raw material vaporizers 36, respectively.

Then, the vacuum chamber 31 is evacuated by an exhaust system 33 to apressure between about 1×10⁻⁴ and 1×10⁻³ Pa, and to a pressure of 2×10⁻⁴Pa, for example. The base 37 is heated to an arbitrary temperature bythe heater provided in the sample holder 35. The base 37 may be heatedto a temperature between room temperature and about 180° C., andpreferably between 160° C. and 180° C.

Then, the PMDA and the ODA are heated by the respective heaters of theraw material vaporizers 36 to a temperature between 160° C. and 180° C.to be vaporized thereby. The vaporized PMDA and ODA react with eachother on the surface of the base 37 to produce a polyamide acid(PMDA+ODA→PAA). This reaction is continued for several minutes, wherebya PAA film with a thickness of several to several tens nm is formed onthe surface of the base 37.

When the base 37 is a structure having the second base 12 mounted on thefirst base 11, the vaporized PMDA and ODA enter the gap (that is, thespace 13) between the first base 11 and the second base 12, whereby aPAA film is formed on the surfaces of the first base 11 and the secondbase 12.

The PAA film formed as described above is heated to about 300° C.(subjected to imidizing heat) whereby the PAA film is changed to PI(polyimide). The heating of the PAA film can be carried out not only ina vacuum, but also in air atmosphere or nitrogen atmosphere. Thecovering layer 15 of polyimide is formed in this manner.

Although the foregoing description has been made of a case in which thecovering layer 15 is formed by chemical reaction between PMDA and ODA,the covering layer 15 may be formed without involving any chemicalreaction. For example, PMDA is vaporized in the same manner as describedabove to form a PMDA layer on the surface of the base 37. Likewise,another organic material (for example, an epoxy resin) is vaporized sothat a molecular layer or thin film thereof is formed on the surface ofthe base 37. In any case, when the base 37 is a structure composed ofthe first base 11 and the second base 12, the vaporized material of thecovering layer 15 will enter the gap between the first base 11 and thesecond base 12 and form the covering layer 15 on the exposed surfacesexposed to the gap.

Further, the covering layer 15 may be formed by using a supercriticaldeposition method. Referring to FIG. 4, a method of forming the coveringlayer 15 by using the supercritical deposition method will be described.

As shown in FIG. 4, a supercritical deposition system has a depositionchamber 41, a heater 42, a back pressure regulator 43, solution feedingpumps 44, 45, 46, and a heat exchanger 47. The deposition chamber 41 isfilled with supercritical CO₂ after a base 48 is introduced into thechamber.

The heater 42, the back pressure regulator 43, the solution feeding pump46 and the heat exchanger 47 are used in order to keep the supercriticalstate of CO₂ in the deposition chamber 41.

The solution feeding pump 46 receives liquid CO₂ at room temperature anda pressure of 6 Pa, for example, and delivers the same at roomtemperature and a pressure of 20 MPa. The heat exchanger 47 changes theCO₂ having room temperature and a pressure of 20 MPa supplied by thesolution feeding pump 46 into a supercritical state at a temperature of80° C. and a pressure 20 MPa, for example, and delivers the same to thedeposition chamber 41. The heater 42 adjusts and maintains thetemperature of the supercritical CO₂ in the deposition chamber 41 whilethe back pressure regulator 43 adjusts and maintains the pressure in thedeposition chamber 41, whereby the supercritical CO₂ in the depositionchamber 41 is kept in a state at a pressure of 20 MPa and a temperatureof 80° C., for example.

When polyimide is deposited to form the covering layer 15, PMDA and ODAas raw materials are dissolved separately in an arbitrary solvent, forexample in DMF (N,N-dimethyl formamide), and the PMDA solution and theODA solution thus obtained are fed into the deposition chamber 41 by thesolution feeding pumps 44, 45, respectively. The PMDA solution and theODA solution are mixed with the supercritical CO₂ in the depositionchamber 41.

On the other hand, the base 48 is being heated to a reactiontemperature, for example to 300° C. by the heater provided in the sampleholder holding the base 48, within the deposition chamber 41. The PMDAand ODA introduced into the deposition chamber 41 react with each otheron the surface of the heated base 48. Since the temperature of the baseis higher than the imidization temperature, the PMDA and the ODA reactwith each other to form a polyimide film.

In this manner as described above, the covering film 15 can be formed bya supercritical deposition method as well. According to this method, thefilm can be formed more uniformly on the exposed surfaces in the gapbetween the first base and the second base.

Next, a second embodiment of this invention will be described withreference to FIGS. 5A and 5B.

FIG. 5A illustrates a state of a stacked LSI, for example a stacked DRAMin the course of its manufacturing process. A plurality of DRAM chips 52are mounted on a mounting board 51 with a distance of 5 to 10 μm fromeach other. When the DRAM chips are stacked with this distance, it willtake a long time or will be difficult to inject underfill using aside-fill method, in general.

Each of the DRAM chips 52 has a plurality of through electrodes (TSVs,or through silicon vias), and these through electrodes are connected tothrough electrodes of other DRAM chip(s) 52 located on and/or under theDRAM chip via bumps 53

The stacked DRAMs in the state as shown in FIG. 5A are very weak inmechanical terms. Therefore, injection of underfill is indispensable toprotect junctions (the bumps 53) and to enhance the mechanical strength(reliability).

The stacked DRAMs in the state as shown in FIG. 5A are introduced into aCVD chamber in the same manner as in the first embodiment. In areduced-pressure atmosphere (or in a vacuum), an epoxy resin material(having no curing agent added thereto) is vaporized as a raw materialfor a covering film having a region with affinity for the underfillmaterial. The vaporized epoxy resin is diffused in the CVD chamber, anddeposited all over the exposed surfaces of the stacked DRAMs to form acovering layer (coating film). The covering layer is formed to athickness of several to several hundred nm. If there is any region wherethe formation of the covering film should be avoided (for example, theupper surface of the uppermost stacked DRAM), such region should bepreliminarily masked.

Next, as shown in FIG. 5B, an epoxy resin (mixed with a curing agent) asan underfill material 54 is injected into space between the mountingboard 51 and the DRAM chips 52 as well as into the spaces between theDRAM chips 52 by means of a side-fill method. Since the covering layerof an epoxy resin is formed on the exposed surfaces of the stacked DRAMsto provide high wettability to the underfill material 54, the underfillmaterial 54 is allowed to quickly enter the spaces between the DRAMchips 52 in spite of narrowness of the spaces. Generation of voids canalso be prevented or reduced. The underfill material 54 is then heatedand cured, and a stacked DRAM is completed.

According to this second embodiment as well, as described in the above,the underfill material can be injected easily in spite of the smalldistance between the DRAM chips (and the DRAM chip and the mountingboard 51), and generation of voids can be prevented or reduced. Thismakes it possible to provide a stacked DRAM having high reliabilitywithout joint failure between the DRAM chips, and without causingelectrical breakdown of the DRAM chips.

Although, in the foregoing description, a covering film having affinityfor the underfill is formed after a plurality of DRAM chips are mountedon a mounting board, the covering film may be formed before mounting theDRAM chips. In this case, if the CVD device shown in FIG. 3, forexample, is used for formation of the covering film, the covering filmis formed on one surface of each DRAM chip at a time. If one surface ofeach DRAM chip is of a material different from that of the othersurface, the covering film may be formed only on the surface that haspoorer compatibility with the underfill. For example, if one surface ofthe DRAM chip is covered with polyimide while the other surface iscovered with a silicon nitride (SiN) film, the covering film may beformed only on the surface covered with the SiN film. Obviously, thecovering film may be formed on both of the surfaces of each DRAM chip.The covering film may be formed of a material having a region withaffinity for the SiN film (for example, a hydroxyl group), and having aregion with affinity (lipophilicity) with the underfill material (forexample, an epoxy resin).

The DRAM chips having the covering film formed on one or both surface(s)thereof are stacked on the mounting board and the underfill material isinjected into the spaces between the stacked DRAM chips, whereby astacked DRAM similar to the one shown in FIG. 5B is obtained.

Although the inventions has been described above in connection withseveral preferred embodiments thereof, it will be appreciated by thoseskilled in the art that those embodiments are provided solely forillustrating the invention, and should not be relied upon to construethe appended claims in a limiting sense. For example, the material ofthe covering film is not limited to an epoxy resin or polyimide, andother organic molecular materials can be selectively used in accordancewith the surface materials of the first and second bases and compositionof a sealing agent. This invention is applicable to not only a deviceincluding a DRAM chip but also various semiconductor devices.

The whole or part of the exemplary embodiments disclosed above can bedescribed as, but not limited to, the following supplementary notes.

(Supplementary Note 1) A method of manufacturing a device, comprising:

forming a covering layer having affinity for a filler to be injectedinto a space between a first base and a second base, on at least one ofthe opposing surfaces of the first base and the second base; and

injecting the filler into the space between the first base and thesecond base.

(Supplementary Note 2) The method of manufacturing a device as describedin Supplementary Note 1, wherein the formation of the covering layer isperformed by vaporizing a material of the covering layer.

(Supplementary Note 3) The method of manufacturing a device as describedin Supplementary Note 2, wherein the formation of the covering layer isperformed with at least one of the first base and the second base placedin a reduced-pressure atmosphere.

(Supplementary Note 4) The method of manufacturing a device as describedin Supplementary Note 1, wherein the filler is an epoxy resin mixed witha curing agent, and the material of the covering layer is an epoxy resinwhich is not mixed with a curing agent.

(Supplementary Note 5) The method of manufacturing a device as describedin Supplementary Note 1, wherein the covering layer is formed ofpolyimide.

(Supplementary Note 6) The method of manufacturing a device as describedin Supplementary Note 1, wherein the filler is injected by utilizingcapillary action.

(Supplementary Note 7) The method of manufacturing a device as describedin Supplementary Note 1, wherein the formation of the covering layer isperformed after the second base is arranged above the first base.

(Supplementary Note 8) The method of manufacturing a device as describedin Supplementary Note, wherein the formation of the covering layer isperformed on at least one of the first base and the second base beforethe second base is arranged above the first base.

(Supplementary Note 9) The method of manufacturing a device as describedin Supplementary Note 1, wherein both of the first base and the secondbase are a semiconductor chip.

(Supplementary Note 10) The method of manufacturing a device asdescribed in Supplementary Note 1, wherein the first base is a mountingboard and the second base is a semiconductor chip.

What is claimed is:
 1. A device comprising: a first base; a second basearranged above the first base to leave a space; a filler disposed in thespace; and a covering layer formed on both of the opposing surfaces ofthe first base and the second base and contacting the filler, whereinthe covering layer is higher in wettability with respect to the fillerthan with respect to at least one of the opposing surfaces of the firstbase and the second base, wherein the covering layer is a polyimidefilm.
 2. The device as claimed in claim 1, wherein both of the firstbase and the second base are a semiconductor chip.
 3. The semiconductordevice as claimed in claim 1, wherein the first base is a mountingboard, and the second base is a semiconductor chip.
 4. A devicecomprising: a first base; a second base arranged above the first base toleave a space; a filler disposed in the space; and a covering layerformed on at least one of the opposing surfaces of the first base andthe second base and contacting the filler, wherein the covering layer ishigher in wettability with respect to the filler than with respect tothe at least one of the opposing surfaces of the first base and thesecond base, wherein the filler is an epoxy resin mixed with a curingagent, and material of the covering layer is an epoxy resin that is notmixed with a curing agent.
 5. A semiconductor device comprising: a firstsubstrate; a second substrate that is stacked over the first substratevia a bump electrode to form a gap between the first substrate and thesecond substrate; a resin layer that is formed in the gap; and a firstcovering layer that is intervening between the resin layer and the firstsubstrate and contacts the resin layer and the first substrate, whereinthe first covering layer is higher in wettability with respect to theresin layer than with respect to the first substrate, wherein the firstcovering layer is a polyimide film.
 6. The semiconductor device asclaimed in claim 5, wherein both of the first substrate and the secondsubstrate are a semiconductor chip.
 7. The semiconductor device asclaimed in claim 5, wherein the first substrate is a mounting board, andthe second substrate is a semiconductor chip.
 8. The semiconductordevice as claimed in claim 5, further comprising: a second coveringlayer that is intervening between the resin layer and the secondsubstrate and contacts the resin layer, wherein the second coveringlayer is higher in wettability with respect to the resin layer than withrespect to the second substrate.
 9. A semiconductor device comprising: afirst substrate; a second substrate that is stacked over the firstsubstrate via a bump electrode to form a gap between the first substrateand the second substrate; a resin layer that is formed in the gap; and afirst covering layer that is intervening between the resin layer and thefirst substrate and contacts the resin layer, wherein the first coveringlayer is higher in wettability with respect to the resin layer than withrespect to the first substrate, wherein the resin layer is an epoxyresin mixed with a curing agent, and material of the first coveringlayer is an epoxy resin that is not mixed with a curing agent.
 10. Thesemiconductor device as claimed in claim 5, wherein the first substrateis larger in size than the second substrate.
 11. The semiconductordevice as claimed in claim 5, wherein the first covering layer isextending from the first substrate to the bump electrode.
 12. Asemiconductor device comprising: a stack structure including a pluralityof substrates stacked over with one another via a bump electrode to formgaps between adjacent ones of the plurality of substrates, thesubstrates including an intermediate substrate sandwiching between thesubstrates, the intermediate substrate having a first surface, a secondsurface opposite to the first surface and a polyimide film formed overthe first surface; a resin layer that is formed in the gaps; and acovering layer provided over the second surface of the intermediatesubstrate, and the covering layer being between the resin layer and theintermediate substrate, wherein the covering layer is higher inwettability with respect to the resin layer than with respect to thesecond surface of the intermediate substrate, and each of the polyimidefilm and the covering layer is in contact with the resin layer.
 13. Thesemiconductor device as claimed in claim 12, wherein the plurality ofsubstrates are semiconductor chips.
 14. The semiconductor device asclaimed in claim 12, wherein a lowermost of the plurality of substratesis a mounting board, and another of the plurality of substrates is asemiconductor chip.
 15. The semiconductor device as claimed in claim 12,wherein a lowermost of the plurality of substrates of the stackstructure is larger in size than another of the plurality of substratesof the stack structure.
 16. The semiconductor device as claimed in claim12, wherein the covering layer is extending to the bump electrode. 17.The semiconductor device as claimed in claim 6, wherein at least one ofthe first substrate and the second substrate includes a throughelectrode that is electrically connected to the bump electrode.
 18. Thesemiconductor device as claimed in claim 12, wherein the covering layeris a polyimide film.
 19. The semiconductor device as claimed in claim12, wherein the resin layer is an epoxy resin mixed with a curing agent,and the covering layer is an epoxy resin that is not mixed with a curingagent.
 20. The semiconductor device as claimed in claim 13, wherein theintermediate substrate includes a through electrode that is electricallyconnected to the bump electrode.